Optical molecular imaging is a rapidly developing technique of molecular imaging, which combines optical process with certain molecular properties. Optical molecular imaging analyzes and processes bioluminescence or excited fluorescence in objectives, and studies them qualitatively and quantitatively.
Representative imaging methods of optical molecular imaging technology are fluorescence imaging and bioluminescent imaging (BLI). Both of them belong to two-dimensional luminescent imaging technology. Although the technology is convenient and simple, it has limitations in application, especially for imaging depth, two-dimensional fluorescence image that may not reflect the information of light source depth and hard to quantify it. The two technologies mentioned above can only reflect projection information of fluorescent probes in organisms at a certain angle, which is generated by superposition of multiple depths signals. So, two-dimensional imaging technology has a very low resolution.
BLT developed based on two-dimensional bioluminescent imaging technology has become an important branch of optical molecular imaging because BLT can reflect the information of signal depth. Bioluminescence tomography technology works not by excitation of an external light source, but by a biochemical luminescence reaction in organisms. Photons generated in organisms propagate in a certain way in the biological tissue and constantly interact with it such as to reach body surface. Finally, distribution of the bioluminescent source in a small animal can be reconstructed using the bioluminescent images acquired on the surface of biological tissue by a high sensitivity detector, which reveals activity laws of molecules in vivo in essence.
The photons in biological tissue do not transmit along a straight line, but experience a lot of scattering process, which leads to BLT inverse problems: a highly ill-posed problem in mathematics. And small measurement disturbance from outside will bring great changes to reconstruction results. The researchers did a lot of work to reduce the ill-posedness usually by providing different prior knowledge to the problem from different angles.
The existing methods reducing ill-posedness are mostly based on multiplying spectral information and sparsity of light sources to study BLT reconstruction methods. However, the correlation among multi-spectra is not considered. In mathematics, the method of multi-spectra increases the known quantity of the equation to be solved, which can improve solving results. For BLT, in the method based on multi-spectra, the light source is reconstructed by the data obtained using multiple filters from different wavelengths, while the light source is remained unchanged. In fact, measurements among multi-spectra are not independent, but interrelated, and their common task is the reconstruction of the bioluminescent source. Therefore, the quality of reconstructed BLT images will be likely improved if the correlation among multi-spectra is considered into reconstruction. Based on this, a BLT reconstruction method based on inner-correlation of multi-spectra is proposed in the disclosure.
The disclosure is based on a multitask learning method. Firstly a high order approximation model is used to model the law of light transmission in the biological tissue, then inner-correlation among multi-spectra is researched based on the multitask learning method, and finally on this basis three-dimensional reconstruction of the bioluminescent source is realized.